The present application relates in general to sub-millimeter devices, and more particularly, to a system and method for fabricating Microelectromechanical (MEM) devices into pre-existing integrated circuits.
MEM devices have many applications for forming any variety of microsensors, microactuators, and other microcomponents. The term xe2x80x9cmicrocomponentxe2x80x9d is used herein generically to encompass sub-millimeter electronic components, sub-millimeter mechanical components, as well as MEM devices and MEM Systems (MEMS) components. The monolithic integration of MEM devices with electronic circuitry has been suggested to increase performance, functionality, and reliability of such microcomponents, in addition to significantly reducing the size and cost of the components. Such electronic circuitry may comprise simple electronic components, such as amplifiers having only a few transistors, to complex electronics, such as microprocessors or microcontrollers. The microcomponents typically act as the sensor that relates information to the electronics for processing in some fashion. Typically, because of the incompatibilities between integrated circuit fabrication techniques and MEM device fabrication techniques, methods for integrating electronic circuits and MEM devices have been suggested which either require complex interleaving of fabrication steps or requiring the fabrication of the MEM device first followed by the electronic circuitry.
U.S. Pat. No. 5,326,726 issued to Tsang, et al., discloses such an interleaved or merged process for fabricating a monolithic chip integrating both electronic circuitry with microstructures. In Tsang, et al., the process described fabricating both the electronic circuitry and the microstructure transducer wherein the steps of fabricating the microstructure transducer are generally interleaved among the steps for fabricating the BIMOS circuitry.
U.S. Pat. No. 5,963,788 issued to Barron, et al., discloses another process that fabricates a high quality MEM device before fabrication of the electronic circuitry. The high quality MEM device of Barron, et al., is produced in a mesa (i.e., a cavity etched within the substrate). The processes described in Barron, et al., for fabricating the MEM device typically involve an annealing step that generally raises the temperature to approximately 1100xc2x0 centigrade for around an hour. Such a high temperature would generally destroy any pre-fabricated electronic circuitry. Thus, the Barron, et at, process requires that the MEMs device be fabricated first.
The problem with the current systems and methods for monolithically fabricating integrating electronic circuitry with MEMs devices is that fabrication processes for the electronics are typically connected or tied in some way to the fabrication of the MEMs device. Therefore, a microcomponent could not be added to existing electronic circuitry. For example, if an integrated circuit chip design includes all of the favorable processing for a certain system, no microcomponents could be added, as they are developed, in order to improve the application of the system.
The present invention is directed to a system and method for fabricating microcomponents onto pre-existing/pre-fabricated integrated electronics. One embodiment of the present invention provides additional process steps after completion of all electronics fabrication that etches through the oxide of the passivation layer to the single crystal silicon (SCS) layer of a silicon on insulator (SOI) integrated circuit (IC). Once at the SCS layer of the existing wafer, any number of microcomponents, such as connectors, receptacles, handles, tethers, fasteners, clasps, latches, probes, actuator arms, and the like may be fabricated onto the chip using relatively low temperature and inexpensive processing; thus, preserving the pre-existing electronics.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.